1. Field of the Invention
Aspects of the present invention relate to a sealing member for a fuel cell, a fuel cell using the sealing member, and a method of manufacturing the fuel cell.
2. Description of the Related Art
A fuel cell is a device that generates electrical energy through an oxidation-reduction reaction between an oxygen gas that is supplied to an oxygen electrode and a hydrogen gas that is supplied to a fuel electrode, producing water as a by-product. A fuel cell is formed of a plurality of unit cells that are connected to each other, wherein each of the unit cells includes an electrolyte membrane, an oxygen electrode, and a fuel electrode.
To increase the power generation efficiency of the fuel cell, the gas transmittance of sealing members respectively disposed on an electrolyte membrane and surrounding parts of the electrolyte membrane must be reduced so that the oxygen gas and the hydrogen gas cannot leak to opposite electrodes in the unit cell.
The unit cell is typically disposed between a pair of separator plates that prevent the unit cells from disconnecting from each other. In this case also, the leakage of the oxygen gas and the hydrogen gas to the other unit cells must also be prevented.
Therefore, in the related art, a technique that uses a fluoride rubber as a gasket of the separator plates has been proposed. For example, Japanese Patent Publication No. 2004-51728 discloses a fuel cell that has an increased lifetime by improving the material of the gasket.
Also, Japanese Patent Publication No. 2005-108565 discloses a seal structure of a fuel cell having a gasket with a modified cross-section shape. However, when the sealing structure of the fuel cell disclosed in Japanese Patent Publication No. 2005-108565 is applied to a fuel cell having a polymer electrolyte membrane, gas leakage of oxygen gas and hydrogen gas cannot be completely prevented. That is, if the polymer electrolyte membrane does not have certain strength when the electrolyte membrane is inserted between the pair of gaskets, there is a possibility of breaking the polymer electrolyte membrane.
The Japanese Patent Publication No. 2005-108565 discloses a method of reducing the gas leakage of oxygen gas and hydrogen gas by stacking a plurality of sealing members having a picture-frame shape around an electrolyte membrane. However, if the sealing members are not bonded as one unit, there is a possibility of gas leakage due to gaps between the sealing members and thus, overall safety is not ensured. If the sealing members are formed of a resin film, the sealing members have flexibility. In such a case, when the sealing members are tightened using a screw when a unit cell is manufactured, there may be distortions in the sealing members. Therefore, there is a high possibility in such a structure of leakage of oxygen and hydrogen gases.